37. A container of mass 25.00 g is found to have a total mass of 45.22 g when a sample of potassium nitrate is added. Determine the number of moles of potassium nitrate added to the container.
38. A rock is found to have a mass of 33.8 g. When placed in a graduated cylinder containing 40.0 mL of water, the level of the water is observed to rise to 43.6 mL. Find the density of the rock.
39. What are the steps for obtaining the mass of an object using a balance?
40. What are the steps for obtaining a desired mass (e.g., 10.00 g) of a substance using a balance?
41. Calculate the number of molecules o hydrogen there are in 10.0 g H2.